Fix presubmit warning for AdditionalGroupingPropertiesForCompat webfeat

This web feature's enum was marked obsolete on
https://crrev.com/c/2518106, but the corresponding mojo entry was not
updated causing the following presubmit warning to trigger:


** Presubmit Warnings **
FeatureObserver enum has been updated and the UMA mapping needs
to be regenerated. Please run update_use_counter_feature_enum.py in
src/tools/metrics/histograms/ to update the mapping.

Change-Id: I6b5aaa40b3c2f5da293bcd54f8cb65fdc222ec9c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2522960Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: John Delaney <johnidel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825077}

third_party/blink/public/mojom/web_feature/web_feature.mojom

@@ -2625,7 +2625,7 @@ enum WebFeature {
   kForceEncodedAudioInsertableStreams = 3294,
   kForceEncodedVideoInsertableStreams = 3295,
   kTransformStyleContainingBlockComputedUsedMismatch = 3296,
-  kAdditionalGroupingPropertiesForCompat = 3297,
+  kOBSOLETE_AdditionalGroupingPropertiesForCompat = 3297,
   kPopupDoesNotExceedOwnerWindowBounds = 3298,
   kPopupExceedsOwnerWindowBounds = 3299,
   kPopupExceedsOwnerWindowBoundsForIframe = 3300,